What Is A Control Variable In A Science Experiment?

A control variable is any factor that is controlled or held constant in an experiment. — A command variable is whatsoever gene that is controlled or held constant in an experiment.

A control variable is whatever factor that is controlled or held constant during an experiment. For this reason, information technology's as well known every bit a controlled variable or a abiding variable. A single experiment may contain many control variables. Unlike the contained and dependent variables, control variables aren't a part of the experiment, but they are important because they could affect the outcome. Accept a look at the difference between a control variable and command group and encounter examples of control variables.

Importance of Control Variables

Recall, the independent variable is the one yous change, the dependent variable is the one you measure in response to this modify, and the control variables are whatever other factors y'all control or hold constant then that they tin't influence the experiment. Command variables are of import because:

They make it easier to reproduce the experiment.
The increase confidence in the outcome of the experiment.

For instance, if y'all conducted an experiment examining the outcome of the colour of low-cal on plant growth, merely you didn't control temperature, it might affect the event. 1 low-cal source might be hotter than the other, affecting plant growth. This could atomic number 82 y'all to incorrectly accept or decline your hypothesis. Equally some other case, say yous did control the temperature. If you did not report this temperature in your "methods" section, another researcher might have trouble reproducing your results. What if yous conducted your experiment at 15 °C. Would you expect the same results at 5 °C or 35 5 °C? Sometimes the potential effect of a control variable can lead to a new experiment!

Sometimes you think you accept controlled everything except the contained variable, but still get foreign results. This could be due to what is called a "misreckoning variable." Examples of confounding variables could be humidity, magnetism, and vibration. Sometimes you tin can place a confounding variable and turn it into a control variable. Other times, misreckoning variables cannot exist detected or controlled.

Control Variable vs Control Group

A control group is unlike from a control variable. You expose a control grouping to all the same weather as the experimental group, except yous change the independent variable in the experimental group. Both the control group and experimental grouping should have the aforementioned command variables.

Control Variable Examples

Anything you tin mensurate or control that is not the independent variable or dependent variable has potential to be a command variable. Examples of common control variables include:

Duration of the experiment
Size and composition of containers
Temperature
Humidity
Sample volume
Pressure
Experimental technique
Chemical purity or manufacturer
Species (in biological experiments)

For case, consider an experiment testing whether a sure supplement affects cattle weight gain. The independent variable is the supplement, while the dependent variable is cattle weight. A typical command group would consist of cattle not given the supplement, while the cattle in the experimental group would receive the supplement. Examples of control variables in this experiment could include the age of the cattle, their breed, whether they are male or female person, the amount of supplement, the style the supplement is administered, how often the supplement is administered, the type of feed given to the cattle, the temperature, the water supply, the time of year, and the method used to record weight. There may be other control variables, also. Sometimes you can't actually control a control variable, simply conditions should be the same for both the control and experimental groups. For case, if the cattle are gratuitous-range, weather might change from day to day, just both groups would have the same experience. When you take data, be sure to record command variables along with the independent and dependent variable.

References

Box, George E.P.; Hunter, William G.; Hunter, J. Stuart (1978). Statistics for Experimenters : An Introduction to Blueprint, Data Analysis, and Model Building. New York: Wiley. ISBN 978-0-471-09315-2.
Giri, Narayan C.; Das, Chiliad. N. (1979). Design and Assay of Experiments. New York, N.Y: Wiley. ISBN 9780852269145.
Stigler, Stephen M. (November 1992). "A Historical View of Statistical Concepts in Psychology and Educational Enquiry". American Journal of Educational activity. 101 (ane): lx–70. doi:10.1086/444032